The B8 5100 ride height adjustable will lift the front of the truck while the 4600 will retain factory ride height.
When deciding whether the B6 4600 or B8 5100 series is best for you, consider do you want to keep the truck/SUV with factory front coil over suspension stock ride height or do you want to lift/level the front? The B8 5100 ride height adjustable will lift the front of the truck while the 4600 will retain factory ride height. If it is already lifted then you will need to use our 5100 shocks. Our 4600 are strictly just for the stock height.
Our B6 4600 shocks are our best riding and driving truck shocks, we always recommend the B6 4600 if it is a stock height vehicle. The B8 5100 is longer and tuned for a lifted application. Neither shock is more durable or better than the other.
The B8 5100 ride height adjustable shock should only be used for those looking to level the truck, if they want to maintain stock height they should use the B6 4600. The B6 4600 will always ride better at stock height vs. the B8 5100 ride height adjustable set at stock height. The B8 5100 ride height adjustable has been tuned for a preloaded coil spring.
Do I need a B8 5160 or a B8 5100 for my application? If the truck is used primarily on road then go with the B8 5100. The 5160 with reservoir will keep the shock cooler when cycled harder and faster during off road use. The 5160 may also has more travel because the internal floating piston is moved to the reservoir. Neither shock will provide a better ride or is better at hauling heavier loads.